Sonar devices that transmit sound waves have been used previously to obtain information about underwater articles, including fish, structures and obstructions, and the bottom. The sound waves travel from a transducer mounted to a bottom surface of the vessel through the water. The sound wave transmits from the sonar devices in diverging patterns. The sound waves contact underwater articles, which create return echoes. The transducer receives the return echoes and the sonar device analyzes the received echoes. A display device displays representations of the received echoes, for locating fish and other underwater articles.
Known side scan sonar devices locate the transducer in a vessel towed by the watercraft (e.g., a “tow fish”). The tow fish is coupled to the sonar display by a long cable. The length of the cable will depend on the depth of the water and other conditions. For typical applications, the length of the cable is 50 feet or more. Moreover, it is not uncommon for the cable to be hundreds or even thousands of feet long. As can be appreciated by some having ordinary skill in the art, a fisherman or recreation user desiring to have side scan images would be hindered by such an arrangement. For example, maneuvering or turning of the watercraft in different directions is difficult, as well as tangling of the sonar cable with fishing or other recreational equipment. Such known tow fish transducers are maintained at a consistent distance from the bottom of the body of water. This distance is intended to provide desired or optimized resolution and field of view. A consistent distance inhibits, if not prohibits, modifying known transducers for side scan applications (or mounting known side scan transducers to watercraft) because the distance between the transducer to the bottom of the water will vary as the watercraft travels due to the varying depth of the water.
Accordingly, it would be advantageous to provide a sonar imaging system that is coupled to the watercraft, rather than being coupled by a flexible cable and towed behind the watercraft. It would also be advantageous to provide sonar imaging system mountable to a motor (such as a trolling motor), a transom of the watercraft, or to the hull of the watercraft. It would also be advantageous to provide sonar imaging system operable at multiple resonant frequencies for optimized performance at varying bottom depths. It would be desirable to provide for a sonar imaging system for mounting to a watercraft having one or more of these or other advantageous features.